The present invention relates generally to improved filter apparatus and more specifically relates to methods and apparatus for sealing flexible filter media such as filter bags in a filter apparatus.
Filter apparatus using cloth or fiber filter media are well-known in the filter industry. In one common type of filter, the filter media is formed into a bag and the filter apparatus is known as a bag filter. In a typical bag filter, a fluid housing having a fluid inlet and a fluid outlet encloses the filter bag and a filter basket utilized to support the bag. The filter basket may be of one of several constructions, including perforated metal forms, wire mesh screens, or simulated mesh screens. The mouth of the filter bag is held at a fixed location proximate the top of the basket by various mechanisms, such as rings formed of springs or rings having a circular cross-section formed in either metal or plastic.
Filter bags may be of a variety of materials, including cotton, polyester, spun fiberglass, nylon, polypropylene, polyethylene, and Teflon.RTM., etc. As a result of their woven construction, filter bags have a fabric thickness which may be in the range of approximately 0.003 inches to 0.160 inches. Also, because of their woven construction and possible thickness, filter bags may exhibit a significant compressibility.
A problem with conventional bag filters is that there is often substantial turbulence in the influent as it enters the mouth of the bag. With conventional securing mechanisms this turbulence has been found to cause deflection of the bag sufficient to allow influent to bypass the bag, and in some cases to cause the retaining ring to leave its seat and to allow the filter bag to collapse within the basket. Such occurrences are critical because any fluid which leaks past the mouth of the bag to the exterior of the bag will not be filtered through the filter media. Because bag filters are often utilized to filter fluids to remove particles as small as three microns, any deficiency in the seal may lead to a substantial reduction in the efficiency of the filtering process. If the bag comes free from the upper portion of the basket, there is a total breakdown of the seal and a failure of the filtering capability of the filter. Accordingly, a critical area in a bag filter is the point at which the mouth of the bag is secured to the top portion of the basket and a seal is formed to prevent the flow of fluid around the bag.
Accordingly, the present invention provides a filter including a new method and apparatus for sealing a flexible filter media such as a filter bag which utilizes a securing ring providing generally line contact with a receiving member to significantly improve the retention of the securing ring within the receiving member and to therefore cause improved securing of the filter bag.